Paclitaxel, together with anthracyclines, is used as an adjuvant therapy in both primary and refractory BC, particularly in basal-like BC and in BCs that have high-risk indications such as premenopausal; ER-, PR- or HER2-negative; large tumors; or patients with lymph nodes involved [10,11,12]. The gene discussed is ESR1; the disease is breast cancer.